LG MB-387W Service Manual - Page 18

COMPONENT TEST PROCEDURE CAUTIONS 1. DISCONNECT THE POWER SUPPLY CORD FROM THE OUTLET WHENEVER REMOVING THE OUTER CASE FROM THE UNIT. PROCEED WITH THE TEST ONLY AFTER DISCHARGING THE HIGH VOLTAGE CAPACITOR AND REMOVING THE WIRE LEADS FROM THE PRIMARY WINDING OF THE HIGH VOLTAGE TRANSFORMER. (SEE PAGE 2-1) 2. ALL OPERATIONAL CHECKS WITH MICROWAVE ENERGY MUST BE DONE WITH A LOAD (1 LITER OF WATER IN CONTAINER) IN THE OVEN. COMPONENTS HIGH VOLTAGE TRANSFORMER (Wire leads removed) TEST PROCEDURE FILAMENT WINDING TERMINAL RESULTS SECONDARY TERMINAL MAGNETRON (Wire leads removed) PRIMARY TERMINAL 1. Measure the resistance. (Ohm-meter scale: Rx1) • Primary winding • Secondary winding • Filament winding 2. Measure the resistance. (Ohm-meter scale: Rx1000) • Primary winding to ground • Filament winding to ground 1. Measure the resistance. (Ohm-meter scale: Rx1) • Filament terminal 2. Measure the resistance. (Ohm-meter scale: Rx1000) • Filament to chassis 5-8 Approx.: 1.4 ohm Approx.: 90 ohm Less than: 1 ohm Normal: Infinite Normal: Infinite Normal: Less than 1 ohm Normal: Infinite